NANNING, Jan. 17 (Xinhua) -- Rising labor costs and a labor shortage in China's coastal regions have led to more Vietnamese illegally crossing the border to seek work in south China, border police said Thursday.

The border-jumpers have created new challenges for law enforcement on the China-Vietnam border, which saw a 20-percent increase in illegal entries and exits in 2012, according to sources with the border control force in south China's Guangxi Zhuang Autonomous Region.

Border police apprehended 3,592 Vietnamese border-crossers in 2012, with a third of them stating that they were seeking jobs in southeast China's coastal regions, the sources said.

Increased demand for short-term laborers during the harvest season has also resulted in increased illegal entry, the sources said.

Border police said they will crack down on illegal entry by intensifying checks of hotels and rented apartments.